Those 100 keys are chosen from a pool of 1000 keys based on custom logic, and are always different.

IT WOULD BE VERY USEFUL TO HAVE THE FUNCTIONALITY OF PURGING BATCH OF SURROGATE KEYS.
It would be both more easy to purge, and more FASTLY since it would go trough all cached objects once with all the batch.

I guess it should also be noted that you can have multiple surrogate-keys per object, up to 16kB of keyspace for keys with a 1kB max size for a single key, so batches might not necessarily be needed if you wanted to do things like tag objects with oh...let's say "css" , "/static" , "build1234" , "v-day" and/or "10Jan2016", it might be easy to create logical groupings that minimize the need for multiple purges.

Echoing the need for this. Drupal 8 has built-in support for cache tags, which is effectively identical to Fastly's cache tags. Drupal 8 very often needs to invalidate multiple cache tags (~ surrogate keys) at the same time.